1. Field of Invention
This invention relates to a reader of digital information record and a digital data reproduction method. More particularly, the invention relates to a magnetic card reader and a magnetic data reproduction method.
The invention relates to a data demodulation method and a demodulator of magnetic record data for demodulating magnetic record data written to various magnetic record media of a magnetic card, etc.
2. Related Arts
Hitherto, a card reader, for example, as shown in FIGS. 35 and 36 has been known as a card reader for reading magnetic data on a magnetic card. A magnetic card reader 901 comprises a slide groove 903 for inserting and sliding a magnetic card 902, a magnetic head 904 for reading magnetic data on the magnetic card 902, and a circuit board 905 for processing a read signal. The magnetic card 902 is formed on a surface with a magnetic stripe 906 where magnetic data is recorded, and the magnetic card 902 is inserted into the slide groove 903, whereby the magnetic head 904 comes in contact with the magnetic stripe 906. To read the magnetic data, the magnetic card 902 is inserted into the slide groove 903 and is slid in the arrow direction in FIG. 35 manually if the magnetic card reader 901 is manual or by a transport roller, etc., if the magnetic card reader 901 is of motor transport type, whereby the relative positions of the magnetic stripe 906 and the magnetic head 904 are moved and the magnetic head 904 reads the magnetic data on the magnetic stripe 906 in sequence. The magnetic data read by the magnetic head 904 is input to a demodulation circuit placed on the circuit board 905 as an analog signal and undergoes waveform shaping in the demodulation circuit and is reproduced as digital data.
A bit tracking system made up of a peak detection circuit and a peak-to-peak interval measuring circuit is generally used as a technique for processing the analog signal read by the magnetic head 904 and converting the analog signal into digital data.
Generally, in record and reproduction apparatus for handling magnetic record media such as a magnetic card, for example, as shown in FIG. 37, magnetic record data information (see FIG. 38(a)) consisting of two types of frequencies (F and 2F) in combination written to a magnetic record medium 911 such as a magnetic card is reproduced as an analog signal by a magnetic head 912, one of signals provided by passing the analog reproduction signal through two amplifiers 913 and 913 undergoes waveform shaping in a comparator 914 to provide binarization data (see FIG. 38(e)), the peak position occurring at the magnetic inversion position of the above-mentioned analog reproduction signal is previously detected by a peak detection circuit 5 comprising a differentiation circuit, an integration circuit, etc., (see FIG. 38(c)), a timing signal (see FIG. 38(f)) at the level corresponding to peak output of the analog reproduction signal is generated by a timing generation circuit 917 in accordance with a peak interval signal (see FIG. 38(d)) provided by waveform-shaping and binarizing the peak position in a comparator 916, the time interval between the adjacent peak positions is counted using a data discrimination circuit or a CPU 918, and the magnetic record data is demodulated based on the interval data provided by counting the time interval.
At this time, in the data discrimination circuit or the CPU 918, reference time xcex1T is set relative to interval data T and the presence or absence of inversion of the signal polarity in the reference time xcex1T is detected, whereby binary determination is made and demodulation data is provided. To perform data demodulation in such a manner, hitherto a bit tracking system, for example, as shown in FIG. 39 has been proposed so as to cope with fluctuations in the transport speed if a magnetic record medium such as a magnetic card is manually transported particularly in a manual record and reproduction apparatus. In the bit tracking system, for interval data Tk (k=1 , 2, . . . ) of the current bit to be demodulated, interval data Tkxe2x88x921 immediately preceding the interval data Tk is used to set reference time xcex1Tkxe2x88x921 (xc2xd less than xcex1 less than 1) and the values are compared with each other in less-than, equal-to, or qreater-than relation. According to the bit tracking system, if fluctuation in the transport speed occurs and slight fluctuation occurs in the bit time interval of the above-mentioned reproduction signal, a reference signal is calculated from the immediately preceding bit, whereby occurrence of erroneous read is prevented.
However, in the above-described bit tracking system, the magnetic data cannot be read if the speed of the magnetic card 902 is remarkably lowered or the magnetic card 902 stops; this is a problem. If the magnetic card reader 901 is manual, it is difficult for a human being to handle the magnetic card 902 at constant speed, and the speed may become low, causing a read error to occur. Particularly, a person unfamiliar with handling the magnetic card may shift the card from one hand to the other during inserting the card. At this time, the magnetic card 902 stops completely and thus a read error occurs. If the magnetic card reader 901 is of motor transport type, a read error may also occur partially because of a collision with the transport roller, etc. If the magnetic card 902 is handled at enough speed, a read error may be caused by a flaw made on the magnetic stripe 906, disturbance noise, etc. If a read error occurs even in a part of the read data, the magnetic card reader 901 in the related art needs to again read the magnetic card 902.
When such a read error occurs, if the manual card reader 901 is a card reader for use with both the magnetic stripe 906 and an IC chip, a case where the operator is prompted to take out the card 902 and the magnetic data is read when the card is taken out or a case where control is transferred to communication processing with the IC chip is possible. However, in the former case, the transition timing to the communication processing with the IC chip does not exist and the operator must be made to again insert the card 902 for the communication processing with the IC chip. In the latter case, if an IC chip does not exist or communications cannot be conducted or the IC chip is not supported, the magnetic data is read again at the taking-out time and processing is continued or the operator must be made to again insert the card 902. As a message for prompting the operator to perform the next operation and error handling are thus provided in agreement with a possible situation, the processor becomes complicated and ease of operation of the card reader also worsens.
On the other hand, placing strict requirements on handling the magnetic card 90 and the quality of the magnetic stripe 906 to prevent such a read error involves a problem from the viewpoint of ease of operation of the card reader.
Also in the bit tracking system with the immediately preceding data as the reference, if the transport speed of a record medium such as a magnetic card fluctuates rapidly, it is made impossible to follow the speed fluctuation and it is feared that erroneous read may be incurred. For example, interval data T4 in FIG. 39 is a xe2x80x9c1xe2x80x9d signal correctly, and essentially the signal polarity should be inverted within the time range of the reference time xcex13T set based on the immediately preceding interval data T3. In fact, however, the time interval may be prolonged largely because the above-described manual system, etc., is adopted; consequently, inversion of the signal polarity does not take place within the time range of the reference time xcex13T and the original correct xe2x80x9c1xe2x80x9d signal is read erroneously as a xe2x80x9c0xe2x80x9d signal. If an automatic system using motor drive is adopted, there is also a possibility that similar erroneous read will occur.
Further, if the passage speed of a magnetic record medium such as a magnetic card relative to the magnetic head 912 becomes rapidly low or the magnetic record medium stops, change in analog reproduction signal caused by magnetic inversion, namely, the peak value magnitude is decreased and the analog reproduction signal change, namely, the time interval between the adjacent peak positions is prolonged. Consequently, for example, in a differentiation circuit, peak detection may become impossible to make because the peak value is small; if an integration circuit is used, a low frequency signal is cut and thus it may be made impossible to make peak detection of a signal with a long time interval and since signal noise is accumulated, low frequency noise appears and peak detection may become impossible to make.
If the passage speed of a magnetic record medium such as a magnetic card rapidly changes or the magnetic record medium stops, the read speed of the immediately preceding interval data Tkxe2x88x921 and that of the current interval data Tk in the bit tracking system described above become drastically different from each other and therefore it is made impossible to make a comparison between the immediately preceding interval data Tkxe2x88x921 and the current interval data Tk, and precise demodulation may become impossible.
It is therefore an object of the invention to provide a magnetic card reader and a magnetic data reproduction method wherein if a usual read error occurs when a magnetic card is read, it is not necessary to again read the magnetic card and handling and processing the card are unified and the erroneous portion can be corrected.
It is an object of the invention to provide a data modulation method of magnetic record data so as to make it possible to stably execute demodulation according to a simple configuration if the transport speed of a magnetic record medium fluctuates.
It is an object of the invention to provide a data modulation method and a demodulator of magnetic record data so as to make it possible to stably execute demodulation according to a simple configuration if the transport speed of a magnetic record medium lowers.
It is an object of the invention to provide a data modulation method of magnetic record data so as to make it possible to execute precise demodulation according to a simple configuration if the transport speed of a magnetic record medium rapidly changes or the magnetic record medium stops.